1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to the method for manufacturing the semiconductor device using a lithography technique.
The present application claims priority of Japanese Patent Application No. 2002-055754 filed on Mar. 1, 2002, which is hereby incorporated by reference.
2. Description of the Related Art
In manufacturing of a semiconductor device such as an LSI (Large Scale Integrated circuit) or a like, a photo-lithography is used as a requisite process so as to produce a fine pattern of a thin film formed on a semiconductor substrate, for example, an insulating film such as an oxide film, or a conductive film such as a wiring film, or a like.
For example, in a case of producing a fine pattern of the insulating film using this kind of photolithography technique, photoresist is coated on the insulating film to form a photoresist film thereon. Next, an exposing process is performed by irradiating the photoresist film with an ultraviolet ray output from a light source such as a laser or a like, through a mask with a specified pattern. After this, a development process is performed to form a photoresist mask having a specified fine pattern, and followed by etching process to produce a fine pattern of the insulating film, using the formed photoresist mask.
Therefore, a fine patterning process of the insulating film is performed by etching processes using this photoresist mask. These photoresist mask formation processes are performed repeatedly in more than one process that requires photolithographic process.
In the case of these formations of each photoresist mask by repeating the processes corresponding with photolithographic processes, the amount of deviation of the photoresist mask formed from the right designed alignment is measured. Though the amount of deviation of the photoresist mask is usually determined depending on the accuracy of a exposure system (equipment), so called repeating procedures are performed since the photolithographic processes according to designed first layer of film are difficult in the case of the amount of deviation is relatively large from the result of the measurement of the amount of deviation. An increase of a cost is unavoidable when the repeating procedures are performed since the number of the processes is increased.
The above measurement of the amount of deviation of the photoresist mask is performed as the followings: firstly a first alignment-measuring mark for the measurement of a aligned side (hereinafter may be referred to as lower alignment-measuring mark) is formed on the semiconductor substrate as a groundwork, secondary the photoresist film is formed on the substrate after the formation of the insulating film which is a first layer of film, thirdly at the same time of the formation of the above photoresist mask exposing and developing the photoresist film, a second alignment-measuring mark for the measurement on a aligning side (hereinafter may be referred to as upper alignment-measuring mark) being comprised by the above photoresist film is formed so that the upper alignment-measuring mark on the aligning side corresponds to and is overlaid on the lower alignment-measuring mark on the aligned side. Then the amount of relative deviation between the upper alignment-measuring mark and the lower alignment-measuring mark is measured by the exposure system using the measurement for the alignment.
Next, with reference to FIGS. 10A, 10B and 10C, a conventional method for manufacturing a semiconductor device, for example, a semiconductor device as shown in FIG. 11 will be explained sequentially as follows. Firstly, as shown in FIG. 10A, and a device forming region 52 and a mark forming region 53 are allocated on a p-type of a semiconductor substrate 51 for example, and a lower alignment-measuring mark 55 is formed in the mark forming region 53 of the semiconductor substrate 51. In the lower alignment-measuring mark 55, a recessed portion 54 whose a planar shape thereof is of almost square fore example as mentioned later is formed in a scribing region 68 as the mark forming region 53 on the semiconductor substrate 51, by performing an etching process or a like. The lower alignment measuring mark 55 may be formed in the regions other than the cell regions, not being restricted to the scribing region 68 (as shown in FIG. 15). Next, a photoresist film 57 is formed by coating the photoresist on all the surface of the insulating film 56, after forming insulating film 56 such as an oxide film throughout on the surface of the semiconductor substrate 51.
As shown in FIG. 10B, using the photolithographic process, at a same time of forming a photoresist mask 59 with a specified pattern in which a photoresist-removed opening portion such as a trench or a hole (hereinafter may be referred to as opening portion) 58 is formed in the device forming region 52, by exposing the ultraviolet ray from a source of light such as a laser through a photomask (not shown) with a specified circuit pattern to the photoresist film 57, and developing an upper alignment-measuring mark 61 corresponding to the lower alignment-measuring mark 55 on the mark forming region 53.
The upper alignment-measuring mark 61 is made up of a photoresist pattern 60 whose plan shape is of square for example, and placed for example in the inside of the lower alignment-measuring mark 55 made up of the recessed portion 54 for example whose plan shape is of square, as mentioned before. In this case, the photoresist mask 59 and the photoresist pattern 60 which are formed on the device forming region 52 and the mark forming region 53 respectively are formed whose film thickness are the same since they are formed by the same procedures.
Next, alignment is checked, so as to make sure whether the photoresist mask 59 having the specified pattern made up of the opening portion 58 is in the right place with the lower pattern. That is, by using the lower alignment-measuring mark 55 formed on the lower layer and the upper alignment-measuring mark 61 formed on the upper layer as shown in FIG. 12, a relative amount of deviation from a right alignment between the lower alignment-measuring mark 55 and the upper alignment-measuring mark 61 in the X-direction (horizontal direction) or in the Y-direction (vertical direction) is measured. This means that the relative deviation between the lower alignment-measuring mark 55 and the upper alignment-measuring mark 61 is optically measured using the upper alignment-measuring mark 61 as mentioned above. Then when the result of the deviation measurement shows that the deviation is within tolerance, the photoresist mask 59 is judged to be formed with great alignment accuracy. An N-type semiconductor region 62 is formed selectively on the semiconductor substrate 51 by implanting ions which are n-type impurities such as phosphorus (P) through the opening portion 58 in the device forming region 52 using the photoresist mask 59, as shown in FIG. 10B. In this process, the above impurity ion is not implanted into the mark forming region 53 due to a masking effect of both of the photoresist film 57 and the insulating film 56, since the photoresist film 57 and the insulating film 56 are formed and stacked on the mark forming region 53. On the other hand, when it is judged that the photoresist mask 59 is not formed in the device forming region 52 with great alignment accuracy, the processing as above is repeated.
The photoresist mask 59 and the photoresist pattern 60 are removed by the method such as ashing, as shown in FIG. 10C. Then, a semiconductor device 63 as shown in FIG. 11 is manufactured, thermally stabilizing the semiconductor substrate 51 including the N-type semiconductor region 62 by annealing. In reality, the semiconductor device 63 is manufactured by repeating the photolithographic process as the above two or more times, the embodiment of a single step out of photolithographic processing for forming the N-type semiconductor region 62 is used to make the explanation simple.
In the manufacturing process of a semiconductor device 63, a plurality of device regions (circuit device regions) having a same circuit pattern are formed on a piece of the semiconductor substrate 51, then finally dicing of the semiconductor substrate 51 is performed on each semiconductor chip on which each device region is formed. In order to form more than one of the device regions on the semiconductor substrate 51 as mentioned above, patterns corresponding to each device region are transferred repeatedly using the mask (reticle mask) in which the patterns are drawn. The pattern repeatedly transferring process as the above is performed, as shown in FIG. 13, generally by using a reducing-projection type of exposure equipment called an aligner, a stepper, or a like, by using a photomask 66 made up of a semiconductor device pattern 65 with the size of four times or five times larger than a final pattern size of a product and the upper alignment-measuring mark 61 (FIG. 14) on an aligning side, and by exposing an ultra-violet ray to the photoresist film formed on the semiconductor substrate 51 through the reducing-projection lens 67. Thus, the semiconductor device pattern 65 and the upper alignment-measuring mark 61 having respectively a final pattern size of a product are formed on the photoresist film by repeating reducing projection exposure and performing a subsequent developing process.
In the repeating transfer processes of patterns as mentioned above, since the upper alignment-measuring mark 61 is used only for the measurement of the deviation of the photoresist mask 59, the upper alignment-measuring marks 61 are formed in regions other than the device forming region 52, that is, in the scribing regions 68 other than a cell region, and are formed in detail for example in four positions around a periphery of the semiconductor device pattern 65 (one-shot-exposing region) as shown in FIG. 14. FIG. 15 is a plan view showing the semiconductor substrate 51 provided with four upper alignment-measuring marks 61 adjacent to the device forming region 52, and formed by performing pattern repeatedly transferring process. The lower alignment-measuring mark 55 and the upper alignment-measuring mark 61 used for the measurement of the deviation of the photoresist mask 59 show the status that each of them is formed on the scribing region 68 for dicing without adversely affecting for forming a semiconductor device. The semiconductor substrate 51 is diced along with X and Y directions of the scribing region 68, and it is divided into each semiconductor chip as mentioned above.
Each of the lower alignment-measuring mark 55 and the upper alignment-measuring mark 61 as shown in FIG. 12 is placed in the scribing region 68 as shown in FIG. 15. Also, the photoresist film is not removed in the scribing region 68 but on the other hand the photoresist film is removed in each device forming region 52, as shown in the same figure. A photoresist-removed region 70 is set on the photoresist film in the scribing region 68 as shown in FIG. 12 so that the photoresist film in the scribing region 68 is removed and that the upper alignment-measuring mark 61 on the upper side is formed on the photoresist-removed region 70.
On the other hand, in the conventional manufacturing processes in the semiconductor device 63 there is a problem that measurement errors in appearance occur in the measurement of the deviation of the photoresist mask 59 using the photoresist film.
In other words, in the conventional method of the manufacturing processes of the semiconductor devices 63, the upper alignment-measuring mark 61 on the upper side making up the photoresist pattern 60 are formed so that the upper alignment-measuring mark 61 are overlaid on the lower alignment-measuring mark 55 using the scribing region 68 on the semiconductor substrate 51 as the mark forming region 53. However, in the conventional process the upper alignment measuring mark 61 on the upper side are formed with no relations to the device forming regions 52 around the scribing region 68 and a data ratio of the photoresist film (a ratio of a removed area to a remaining area).
Therefore, there occurs a phenomenon that the photoresist pattern 60 making up an arbitrary upper alignment-measuring mark 61 becomes deformed to be asymmetrical in a cross sectional shape, under the influence of an adjacent photoresist pattern making up another upper alignment-measuring mark 61, or of the photoresist film remaining in the scribing region 68 as shown in FIG. 16,
The deformation (loss of its shape) of the photoresist pattern 60 making up the upper alignment-measuring mark 61 becomes remarkable as materials being different from each other or thickness of the photoresist film being thick. This tendency suggests that the deformation of the photoresist pattern 60 will be large considering the fact that the photoresist mask 59 is used in the ion impurities implantation process which is one of the main processes in manufacturing the semiconductor device such as LSIs, particularly deep ion impurities implantation process is required according to the recent tendency of high performance of LSIs, and a thick photoresist film for more than 4 μm is required according to this trend.
Thus, a margin of error in appearance occurs since the alignment of the photoresist mask is measured incorrectly as if a place difference of the photoresist mask 59 is occurred more than that of the actual difference in the measurement of the place difference of the photoresist mask 59 when the photoresist pattern 60 making up the upper alignment-measuring mark 61 changes its shape. A misconception of the margin of error in appearance as the actual place difference occurs in the manufacturing process of the semiconductor device when such a margin of measurement error in appearance occurs. Therefore, productivity of the semiconductor device becomes lower since unnecessary reprocessing is to be performed.